I can suggest two possible fraud scenarios. First, there's a possibility the checks are counterfeits, although actual counterfeits of Treasury checks are few and far between.
The second scenario involves filing multiple tax returns to defraud the IRS. It takes a while for the IRS to catch this kind of scam.
If you have images of the three checks, you can contact the IRS Criminal Investigation Division to pass on any suspicions. In the event that a total of $5,000 or more is involved, you should file a SAR.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8